I. Field
The following description relates generally to wireless communications and, amongst other things, to scheduling resource assignments to user devices in a wireless network environment.
II. Background
Wireless networking systems have become a prevalent means by which a majority of people worldwide has come to communicate. Wireless communication devices have become smaller and more powerful in order to meet consumer needs and to improve portability and convenience. The increase in processing power in mobile devices such as cellular telephones and access terminals has led to an increase in the types of applications, and their complexity, available for use in wireless communication systems. These services all have different requirements for bandwidth and latency.
Wireless communication systems generally utilize different approaches to generate transmission resources in the form of channels. These systems may be code division multiplexing (CDM) systems, frequency division multiplexing (FDM) systems, and time division multiplexing (TDM) systems. One commonly utilized variant of FDM is orthogonal frequency division multiplexing (OFDM) that effectively partitions the overall system bandwidth into multiple orthogonal subbands. These subbands are also referred to as tones, carriers, subcarriers, bins, and frequency channels. Each subband is associated with a subcarrier that can be modulated with data. With time division based techniques, a band is split time-wise into sequential time slices or time slots. Each user of a channel is provided with a time slice for transmitting and receiving information in a round-robin manner. For example, at any given time t, a user is provided access to the channel for a short burst. Then, access switches to another user who is provided with a short burst of time for transmitting and receiving information. The cycle of “taking turns” continues, and eventually each user is provided with multiple transmission and reception bursts.
CDM based techniques typically transmit data over a number of frequencies available at any time in a range. In general, data is digitized and spread over available bandwidth, wherein multiple users can be overlaid on the channel and respective users can be assigned a unique sequence code. Users can transmit in the same wide-band chunk of spectrum, wherein each user's signal is spread over the entire bandwidth by its respective unique spreading code. This technique can provide for sharing, wherein one or more users can concurrently transmit and receive. Such sharing can be achieved through spread spectrum digital modulation, wherein a user's stream of bits is encoded and spread across a very wide channel in a pseudo-random fashion. The receiver is designed to recognize the associated unique sequence code and undo the randomization in order to collect the bits for a particular user in a coherent manner.
A typical wireless communication network (e.g., employing frequency, time, and/or code division techniques) includes one or more base stations that provide a coverage area and one or more mobile (e.g., wireless) terminals that can transmit and receive data within the coverage area. A typical base station can simultaneously transmit multiple data streams for broadcast, multicast, and/or unicast services, wherein a data stream is a stream of data that can be of independent reception interest to a mobile terminal. A mobile terminal within the coverage area of that base station can be interested in receiving one, more than one or all the data streams carried by the composite stream. Likewise, a mobile terminal can transmit data to the base station or another mobile terminal. In these systems the bandwidth and other system resources are assigned according to a scheduler.
In addition, in a typical communication network, information is assigned to different levels of service based upon the application or service for which the information is utilized. For example, certain applications, such as voice or video generally require low latency while others such as simple data requests may have higher allowable latencies.
The purpose of a scheduler in a communication system is to multiplex the data from users to the bandwidth for multiple transmissions. The scheduler may multiplex the users' transmissions over the time, frequency, code, and/or space. The goals of a scheduler are to maximize the system capacity (throughput) while maintaining a specified level of fairness among users and/or throughput for each user. In addition, the scheduler would like to provide service to particular users that best serves the applications that are running on the user's connection, e.g. the service or application being provided. For example, the scheduler would like to meet latency targets for connections that are running latency sensitive applications. The scheduler goals above are often conflicting, and a particular scheduler may emphasize certain goals (such as overall sector capacity).
In view of at least the above, there exists a need in the art for a system and/or methodology of improving wireless communication and frequency resource allocation to users in a wireless network environment.